Russia has denied interfering with evidence at the site of the suspected poison gas attack in Syria, which led to targeted strikes by forces from the United States, United Kingdom and France.

Key points:

The US has told the global watchdog that Russia may have tampered with the site

Russia's Foreign Minister has denied the allegations

The UK says inspectors have not been granted access to the sites yet

"I can guarantee that Russia has not tampered with the site," Russian Foreign Minister Sergei Lavrov told the BBC in an interview.

Inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) will be allowed to visit the site in Douma on Wednesday (local time), Russian Defence Ministry official Igor Kirillov told a news conference in The Hague.

The US and Britain have accused Russia of blocking international inspectors from reaching the site of the suspected attack, in which dozens of people were allegedly killed, and said Russians or Syrians may have tampered with evidence on the ground.

Britain's delegation to the OPCW had earlier accused Russia and the Syrian Government of preventing the international watchdog's inspectors from reaching Douma.

"The inspectors aim to collect samples, interview witnesses and document evidence to determine whether banned toxic munitions were used, although they are not permitted to assign blame for the attack," the British delegations said in a statement.

May faces criticism

In the aftermath of the alleged chemical attack, the remnants of the rebel army evacuated, handing Syrian President Bashar al-Assad one of the biggest victories in a war that has killed about half a million people and laid waste to whole cities.

The US-led strikes did nothing to alter the strategic balance or dent Mr Assad's supremacy and the Western allies have said the aim was to prevent the further use of chemical weapons, not to intervene in the civil war or topple Mr Assad.

In London, British Prime Minister Theresa May is facing criticism over her decision to bypass Parliament and take part in the air strikes.

Jeremy Corbyn, leader of the main opposition Labour Party, has questioned the legal basis for Britain's involvement.

Britain has said there are no plans for future strikes against Syria, but Foreign Secretary Boris Johnson warned Mr Assad that all options would be considered if chemical weapons were used against Syrians again.